We extend the Eclipse IDE with tools for development in Haskell, a functional programming language, providing support for a wide range of tools (compilers, interpreters, doc tools etc.) in a coherent, convenient and configurable environment.

ShellEd is a superb shell script editor for Eclipse. The benefits of this plugin are the integration of man page information for content assist/hover help and the ability to run your project's shell scripts without leaving Eclipse. Check it out!

PyDev is a Python Development Environment (Python IDE plugin for Eclipse).
It features an editor with code completion, code analysis, refactoring, outline view, debugger, mark occurrences and other goodies - check http://pydev.org for more details).
It's kept going by community contributions, so, if you think it's a worthy project, please contribute through http://pydev.org

Open tool platform for the cost effective rigorous development of dependable complex software systems services. This platform is based on the event-B formal method and provides natural support for refinement and mathematical proof.

JAutodoc is an Eclipse Plugin for automatically adding Javadoc and file headers to your source code. It is possible to define Velocity templates for Javadoc and file headers. Update Site: http://jautodoc.sourceforge.net/update/

The Software Testing Automation Framework (STAF) is a framework designed to improve the level of reuse and automation in test cases and test environments. The goal of STAF is to provide a complete end-to-end automation solution for testers.

JGraphT is a free Java class library that provides mathematical graph-theory objects and algorithms. JGraphT supports a rich gallery of graphs and is designed to be powerful, extensible, and easy to use.

AVR-Eclipse is a plugin for the Eclipse IDE which adds toolchain support, through CDT, for the gcc compiler for the Atmel AVR series of microcontrollers, and adds a toolbar button to allow quick upload of produced code to a target device.

qooxdoo is a universal JavaScript framework for creating applications for a wide range of platforms. It has a comprehensive feature set, including an object-oriented programming model, an integrated tool chain and a state-of-the-art GUI toolkit.
Note:
Please note that as of 2011-10-26 the code repository for the project has been moved to https://github.com/qooxdoo/qooxdoo. The existing SVN repository will be set to read-only for the time being, and will not see any more updates.

Rifidi is a middleware and development platform for RFID. With Rifidi you can prototype an RFID application down to the core RFID Hardware and using Rifidi Edge you can easily develop business rules to turn RFID events into real business applications.

Eclipse Verilog editor is a plugin for the Eclipse IDE. It provides Verilog(IEEE-1364) and VHDL language specific code viewer, contents outline, code assist etc. It helps coding and debugging in hardware development based on Verilog or VHDL.

Implementation of DCOM wire protocol (MSRPC) to enable development of Pure Bi-Directional, Non-Native Java applications which can interoperate with any COM component.The implementation is itself purely in Java and does not use JNI to provide COM access.

(Diver is in the process of being moved to GitHub. Please find us at https://github.com/thechiselgroup/Diver. Support requests & messages sent here may never be seen.)
Dynamic Interactive Views For Reverse Engineering. Div/er is a set of Eclipse Plugins that aid developers in understanding software. It uses dynamic analysis and reverse engineering to offer views and filters that aid comprehension and discovery.

A framework and runtime environment for exploring agent-based models designed to support the definition of models using an expressive, high-level and extensible Java API and to support the exploration of these models in both interactive and batch mod